Saturday, 7:00am-9:00am

The usual crew was out in full force this morning, chirping and sitting on the electrical cords, since fairly early in the morning. Maybe they are less likely to leave because the street is quieter on Saturday. There is, however, one couple that flies together everywhere, courting and playing each other, which I find interesting. Apparently, we're at the very end of mating season, so it's not impossible that some late bloomers are still pairing up and getting ready.

Odds are that these folks are not mates for life, but it's not entirely impossible. Carola Haas found that, while robins are not lifetime monogamists, there are some "repeat players" who meet and mate again the following year, especially if their previous mating stint had been successful. If this couple decide to mate and build a nest, even this late in the game, they'll have lots of great spots to choose from.

They'll have to consider the location pretty carefully, because predators abound (and by that I mean birds, not Spade and Archer.) I've read about an interesting experiment conducted by Ian McLean, James Smith and Glenna Stewart, who examined mobbing behavior among nesting robins. When robin couples mob nest predators, one of the unfortunate side effects is that their mobbing calls are a cue to one of their worst predators, the northwestern crow. So, robins have to balance the costs and benefits of mobbing behavior. After confirming that robins mob human "predators" similarly to crow ones, McLean et al. "mobbed" nests of the same couple during the same nesting cycle, or in subsequent nesting cycles. They found that, in the course of the same nesting effort, the robins' response is fairly constant, but across nesting cycles it changes, indicating that mobbing is not just an expression of a particular robin's aggressive character but an outcome determined by many environmental factors, including nest location. The experiment did not find a correlation between mobbing behavior and nesting success, but since the "mobbers" were the humans controlling the experiment that does not surprise me; it very well may be that, in real life, where mobbing or not mobbing has real repercussions, robins are evolutionarily programmed to mob or not mob with the potential effect of mating success in mind.

As I came to the end of today's shift, only one bird remained on the electric cords (it's a beautiful specimen with gorgeous, shiny bronze plumage on its little chest) , but the other birds, including, possibly, the couple, are not far away, judging from the chirps. At this point I can already tell the robin chirps from everyone else's, even though whenever something exciting happens in the yard or out in the street everyone emits an alarm call at more or less the same time. Even though the alarm calls are emitted to protect one's own species, they are probably taken as cues by other types of birds who then emit alarm calls of their own to their own family members.

Chirps in the Distance, Friday, 7am-9am

At 7am there were two robins on the electrical cords. They were fairly quiet until a few other small birds joined them. Then, everyone started singing together. I can identify six different songs, including the robin song, even though I can't see all the varieties. I can't record them, but I can try and transcribe them:

"kakakakakakaka"
"tweet tweet" (there are at least two different pitches I can here, which might belong to different varieties of birds or to two individuals of the same species.)
"papao pa, papao pa" (those are doves)
"Aa Aa Aa" (these are two syllables each, with the first syllable higher in pitch than the second one)
"pip pip pip pipipipip"
"kaaaaaaa kaaaaaaa" (each of these has a downslurring pitch)

[Aside #1: I remember having a birding guide that included similar verbal transcriptions of the bird sounds and thinking it was a fairly poor system of conveying sounds. It turns out that now people use audio pitch tracers, which can render the songs into MIDI files and then transcribe them as sheet music. That also enables them to test for frequency, volume, pitch, etc. For a place like my backyard, you'd need an editing system that would enable you to isolate the song of the particular bird from those of other birds]

[Aside #2: 20th century composer Olivier Messiaen transcribed and used actual birdsongs for his piece Oiseaux Exotiques. Very cool!]


[Aside #3: when the house predators chatter at the birds, are they trying to imitate them? The chatter pattern changes quite a bit, but since I'd been listening to it from the perspective of the cats, not of the birds, I hadn't sought a mimicry explanation. Now that I'm focusing on the birds, I should remember to pay attention in the future to what exactly it is that the predator at home is responding to.]

UPDATE: Despite there being no activity on the electric cords, I stayed until 9am and listened to the songs, which continued in the same pattern. I also noticed interesting things about flight, which I'll detail in the next post.

Chirping on a Thursday Morning: 8-10am

This morning included several interesting events. It started, like every morning at Casa Corazones, with loud morning singing by the birds. I'm not sure whether the singing subsides in the later morning or the human noises drown it out. But the singing definitely changes character in response to events in the yard.

I've heard four different types of chirps today, but it's interesting that they often converge. I assume all birds need to warn their friends of a coming predator (communication) with the perhaps-unintended consequence of warning other birds, too (cue). The chirping intensified twice: when Spade got on the rosebush and when my neighbor walked her dog down the street. At that point, all the birds sounded what seemed to be a loud alarm.

This little guy positioned himself right above the fence, emitting tweets in alternating singles and pairs: "tweet, tweet tweet, tweet, tweet tweet".


He then flew up to a safer distance from the predator and continued singing, albeit with lesser frequency.

I wonder if there's a relationship between the intensity and frequency of the tweets and the proximity to the predator. And if there is one, is it linear? exponential? does the urgent chirping stop when one is at a safe distance?

After the predator got off the rosebush, the tweeter was joined by several friends. The tweets changed from the single-double pattern to a single pattern.

Then, a new pattern emerged: fast chirps in a row ("tweet-tweet-tweet-tweet-tweet") and the entire host flew away--which could be related to my neighbor's mighty Harley roaring down the street. The host relocated to a new spot on the telephone pole, but left fairly quickly.

I'm impressed with how difficult it is to find a safe resting place when you're a small bird. Everything is frightening and dangerous and you're constantly on the move, sort of like a film noir character.

(as an aside: one cabbage butterfly, two hummingbirds, one butterfly with black and orange wings, two bees.)